Interaction between the ultrashort pulse and two-level medium beyond the rotating wave approximation Long-Zhao Lu, Da-Qing Wen, Shao-Ji Jiang and Xiang-Yang Yu Eur. Phys. J. D, 70 9 (2016) 184 Published online: 06 September 2016 DOI: 10.1140/epjd/e2016-70038-4